Drilling and completion operations for creating a well bore transporting oil and gas from a downhole location to surface have an associated risk of leakage of hydrocarbons into the environment or in a worst-case scenario, a catastrophe such as an explosion and consequential loss of life.
Safety devices are provided in well bores to allow the well to be shut down and sealed in the event of an emergency situation. The most commonly used safety device is the blowout preventer (BOP) which is mounted on the wellhead. The BOP has a number of closure devices such as rams which come together when required to form a seal and contain the well.
If the BOP fails or there is a breach below the BOP, hydrocarbons can be released and it can be very difficult to recover the situation.
Other methods of closing or restricting the flow through a well bore have been disclosed such as the collapsible casing device disclosed in WO2012/058544, the contents of which are incorporated herein by reference. The device described in this document uses an explosive charge located behind the deformable insert to reduce or restrict the diameter of the well bore by deforming the insert into the well bore under the effects of the explosive charge. The deformable insert described in WO'544 has to have sufficient strength to withstand well pressure to protect explosive material from being compressed.